diff --git a/hal/tests/TESTS/mbed_hal/stack_size_unification/main.cpp b/hal/tests/TESTS/mbed_hal/stack_size_unification/main.cpp
index c430137..8d125a7 100644
--- a/hal/tests/TESTS/mbed_hal/stack_size_unification/main.cpp
+++ b/hal/tests/TESTS/mbed_hal/stack_size_unification/main.cpp
@@ -37,7 +37,9 @@
 
 #define EXPECTED_USER_THREAD_DEFAULT_STACK_SIZE  (MBED_CONF_RTOS_THREAD_STACK_SIZE)
 
-#if ((MBED_RAM_SIZE - MBED_CONF_TARGET_BOOT_STACK_SIZE) <= (EXPECTED_MAIN_THREAD_STACK_SIZE + EXPECTED_ISR_STACK_SIZE))
+#ifndef MBED_RAM_SIZE
+#error Target must define MBED_RAM_SIZE!
+#elif ((MBED_RAM_SIZE - MBED_CONF_TARGET_BOOT_STACK_SIZE) <= (EXPECTED_MAIN_THREAD_STACK_SIZE + EXPECTED_ISR_STACK_SIZE))
 #error [NOT_SUPPORTED] Insufficient stack for stack_size_unification tests
 #endif
 
diff --git a/targets/TARGET_NXP/TARGET_LPC176X/device/cmsis_nvic.h b/targets/TARGET_NXP/TARGET_LPC176X/device/cmsis_nvic.h
index 2ea4323..24d51c6 100644
--- a/targets/TARGET_NXP/TARGET_LPC176X/device/cmsis_nvic.h
+++ b/targets/TARGET_NXP/TARGET_LPC176X/device/cmsis_nvic.h
@@ -34,4 +34,6 @@
 #define NVIC_NUM_VECTORS        (16 + 33)
 #define NVIC_RAM_VECTOR_ADDRESS 0x10000000    // Location of vectors in RAM
 
+#define MBED_RAM_SIZE 0x7F18 // Linker script defines main RAM as 32K - 0xC8 - 32
+
 #endif